The present invention relates in general to bicycles, and, more particularly, to bicycle brakes.
The problems and/or obstacles faced in the design and/or construction of bicycle brakes have been as follows:
1. Because a bicycle is human-propelled, extreme lightweight constuction is of paramount importance. This requirement applies to all parts of a bicycle, and thus also applies to the brake mechanism and to all parts of the bicycle to which the brakes are attached. PA1 2. For a brake to function effectively, that brake must be quite rigid, resisting rather high forces that tend to bend or twist the brake parts. PA1 3. To function efficiently, the brake should offer maximum retardation with minimum hand effort and minimum hand movement. PA1 4. Because the design and construction of bicycles has become very standardized, and industry custom has been to provide component parts that are interchangeable among almost all bicycles, the design of brakes (or any other components) has been limited or restricted by having to fit onto existing bicycles. PA1 5. In the case of caliper brakes, the mounting system includes a 6 millimeter diameter (0.236") bolt fitting through 6 mm (or slightly oversized) holes in the front fork and rear brake bridge. PA1 6. In order to simplify construction, reduce the number of separate parts, and thereby lower costs, it has been customary to use the 6 mm bolts as the pivot bearings on side-pull type brakes (the type preferred by more critical cyclists). Such a small diameter bearing is necessarily less wear-resistant than a larger one would be, and more susceptible to stretching or elongation when used hard. Also, clearances are more critical.
These requirements conflict with one another, to the point of making a really efficient brake almost an impossibility. The 6 millimeter bolt, even though made of steel, is too flexible and flexes upward at the front wheel or downward at the rear wheel when the brake is applied. One solution would be to use a larger diameter (and therefore stiffer) bolt. However, the 6 mm hole is in the fork crown (probably the most highly stressed part on a bicycle), and any significant enlargement of this hole would weaken the fork crown. At the rear the thin, lightweight brake bridge is so small that even a 6 mm hole removes more than half the cross-section of said brake bridge, and any significant increase in hole size would further weaken an already delicate member.